Conventional processes for preparing fine particle pharmaceutical formulations by extrusion/spheronization involve the steps of blending the dry ingredients which make up the formulation, wetting the dry powdered blend, extruding the resulting wetted blend, and forming the extrudate into fine particles by spheronization.
Generally, the size of particles produced by the above method is limited to particle sizes ranging above about 0.5 mm. Moreover, the amount of water added in the wetting step must be carefully controlled. Excess water causes the extrudate in the extrusion step to take on the consistency of "mud" while too little water causes the wetted material to rupture the screens of the extrusion equipment. The result is that without very careful process control of the amount of water added to the formulation in the wetting step, batches may be unacceptable with attendant loss of time and/or money.
There is thus a need for a convenient, cost-effective and efficient method for making fine particle pharmaceutical formulations which overcome the disadvantages inhenent in prior art methods.